Anti-angiogenic therapy promises to be a powerful tool for the treatment of solid tumors: drug resistance is less likely to develop and such therapy may be effective in a broad range of tumor types. A diverse array of compounds have been described which possess anti-angiogenic action. The subclass of these that are proteins have attracted considerable attention because of their ability to regress tumors. These have also turned out to be fragments of naturally occurring proteins. However, certain limitations exist for the use of these known proteins for therapy; namely, that delivery cannot be oral, and that large amounts are currently needed for efficacy. With regard to the latter, there is, therefore, a need to identify compounds with greater potency. This proposal focuses on the isolation and initial characterization of factors derived from human ovarian cancer ascites and conditioned medium (CM) from an ovarian cancer cell line. In preliminary studies, the PI has identified a gel filtration fraction of this ascites and CM, which shows remarkable activity towards endothelial cells in both proliferation and migration assays. The activity is heat and protease labile, suggesting that it is a protein. Furthermore, this activity is at least a 1000 fold more potent than endostatin. Specific Aim 1: Purification of anti-angiogenic agent from ovarian cancer CM Specific Aim 2: Functional characterization of the anti-angiogenic agent(s) These findings may have major therapeutic implications, in that they will provide an alternative source for powerful anti-angiogenic compounds. Moreover, an understanding of the mechanism of action will allow for the optimal and rational use in tumor therapy, in combination with other angiostatic agents or chemo- or radiation therapy. Such agents would be useful not only in tumor therapy, but in other angiogenesis dependent disease states, as well.